1. Field of the Invention
The present invention relates to a high-frequency module including a plurality of filter elements.
2. Description of the Related Art
A device having a wireless communication function, such as a mobile device, includes a filter circuit to allow only high-frequency signals of a desired frequency to pass therethrough and to attenuate high-frequency signals of frequencies other than the desired frequency.
One example filter circuit including a plurality of surface acoustic wave (SAW) filters is described in Japanese Unexamined Patent Application Publication No. 2012-109818. Specifically, the filter circuit in Japanese Unexamined Patent Application Publication No. 2012-109818 is one in which the plurality of SAW filters are connected in series between input and output terminals. The filter circuit further includes SAW filters disposed between the ground and the connection lines connecting the plurality of SAW filters connected in series.
In the filter circuit described in Japanese Unexamined Patent Application Publication No. 2012-109818, an inductor or a series circuit including an inductor and a capacitor (referred to as a correction circuit) is connected in parallel to the series circuit of the SAW filters. The correction circuit is adjusted such that a high-frequency signal having a frequency outside the pass band and passing through a circuit unit including the group of SAW filters (signal to be suppressed) and a signal to be suppressed passing through the correction circuit have the same amplitude and opposite phases. The signals to be suppressed are cancelled out at the connection between the circuit unit including the group of SAW filters and the correction circuit, and these signals are not output from the output terminal.
However, the above-described configuration needs to include a correction circuit consisting of the inductor or of the series circuit including the inductor and the capacitor prepared only for improving the attenuation characteristic, in addition to the main circuit unit including the group of SAW filters having the filter function.
Accordingly, the number of components in the filter circuit is large, the size of the filter circuit is increased, and it is unsuitable for current devices such as mobile terminals where miniaturization is desired.